Bi-steric mTORC1 inhibitors induce apoptotic cell death in tumor models with hyperactivated mTORC1
Heng Du, … , Mallika Singh, David J. Kwiatkowski
Heng Du, … , Mallika Singh, David J. Kwiatkowski
Published November 1, 2023
Citation Information: J Clin Invest. 2023;133(21):e167861. https://doi.org/10.1172/JCI167861.
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Research Article Oncology

Bi-steric mTORC1 inhibitors induce apoptotic cell death in tumor models with hyperactivated mTORC1

Abstract

The PI3K/AKT/mTOR pathway is commonly dysregulated in cancer. Rapalogs exhibit modest clinical benefit, likely owing to their lack of effects on 4EBP1. We hypothesized that bi-steric mTORC1-selective inhibitors would have greater potential for clinical benefit than rapalogs in tumors with mTORC1 dysfunction. We assessed this hypothesis in tumor models with high mTORC1 activity both in vitro and in vivo. Bi-steric inhibitors had strong growth inhibition, eliminated phosphorylated 4EBP1, and induced more apoptosis than rapamycin or MLN0128. Multiomics analysis showed extensive effects of the bi-steric inhibitors in comparison with rapamycin. De novo purine synthesis was selectively inhibited by bi-sterics through reduction in JUN and its downstream target PRPS1 and appeared to be the cause of apoptosis. Hence, bi-steric mTORC1-selective inhibitors are a therapeutic strategy to treat tumors driven by mTORC1 hyperactivation.

Authors

Heng Du, Yu Chi Yang, Heng-Jia Liu, Min Yuan, John M. Asara, Kwok-Kin Wong, Elizabeth P. Henske, Mallika Singh, David J. Kwiatkowski

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Figure 1

Bi-steric mTOR inhibitors show potent inhibition of tumor cell proliferation.

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Bi-steric mTOR inhibitors show potent inhibition of tumor cell prolifera...
(A and B) Growth inhibition curves of TSC1-null HCV29 cells (A) and TSC1–add-back HCV29 cells (B) treated with rapamycin, MLN0128, RMC-4627, and RMC-6272. Each dot and error bar on the curves represent mean ± SD (n = 6). (C) Cell proliferation rate of HCV29 TSC1-null cells treated with rapamycin (1 nM), MLN0128 (10 nM), RMC-4627 (1 nM), and RMC-6272 (1 nM) for 24 hours followed by washout. Each dot and error bar on the curves represent mean ± SD (n =6). (D) Cell cycle analysis of HCV29 TSC1-null cells treated with rapamycin (1 nM) or RMC-6272 (1 nM) for 24 hours. (E and F) Long-term low-dilution clonogenic growth assay of TSC1-null HCV29 (E, left) and TSC1–add-back HCV29 (E, right) cells, and quantification of clone numbers (F). Each bar is the median of n = 3 measurements. One-way ANOVA was used. *P < 0.05, ***P < 0.001, ****P < 0.0001. (G) The effect of rapamycin, MLN0128, RMC-4627, and RMC-6272 on mTORC1 signaling in HCV29 TSC1-null cells treated with different concentrations (nM) of inhibitors for 4 hours. (H) The effect of rapamycin, MLN0128, RMC-4627, and RMC-6272 on mTORC1 signaling in HCV29 TSC1-null cells treated as in C for 24 hours followed by washout.